1. Field of the Invention
The present invention relates to a method of manufacturing an electronic device having a molded resin case and a molding tool for forming the resin-molded case.
2. Description of the Related Art
JP-5-21492A discloses a hybrid integrated circuit (hybrid IC) that includes a hybrid IC board and a resin film for sealing the hybrid IC board. The resin film is formed using a molding tool including an upper molding element and a lower molding element. The lower molding element includes a plurality of holding parts protruding to a molding space from a lower portion thereof. The holding parts are movable in an up-and-down direction. The hybrid IC board includes a lead wire. The hybrid IC is disposed on the holding parts while the lead wire is inserted into a receiving groove. Then, melted resin is filled into the molding space through an introducing passage and a submarine gate. When a most of the molding space is filled with the melted resin, the holding parts move downward. Then, the molded resin is further filled into the molding space while applying a predetermined pressure. In this way, the resin film for sealing the hybrid IC board is formed.
When electronic elements mounted on the hybrid IC board are directly sealed by the resin, the electronic elements or a connecting portion between the electronic elements and the hybrid IC board may be damaged depending on a property of the resin. For example, stress or thermal stress is applied to the hybrid IC when the resin film is formed. Thus, the electronic elements mounted on the hybrid IC are housed in a circuit casing, and the circuit casing is sealed with resin. However, when the melted resin is filled into the molding space, the hybrid IC board and the circuit casing receive a filling pressure. Thereby, the hybrid IC board may deform and a clearance is provided between the hybrid IC and the circuit casing. In the present case, the electronic elements cannot be sealed by the circuit casing. Thus, an additional process, for example, an adhesion process is required for fixing the circuit casing to the hybrid IC board.